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Sunday, November 29, 2009

Watt Meter Measurements, 30-35Wh/Mile

I finally got the chance to use one of those Turnigy Watt Meters to test some stuff on the CrazyBike, and it's nice enough, but I wish it measured current in reverse. It does allow reverse current flow with no problems, it just doesnt' register it. (I can charge the battery with it hooked up charger on motor plug of meter).

Now I know that my bike on a typical workday ~5-mile trip uses around 30Wh/mile on the 2.3 mile home-to-work trip, and about 35Wh/mile on the 2.5 mile work-to-home trip, loaded down with an additional 80-ish pounds of stuff in the cargo pods, including a 40-pound bag of dog food. I guess since it's hauling 300 pounds of bike and me, plus that stuff, it's not that bad.

This includes about two miles (one each way) at 17-18MPH, some of that into a stiffish headwind (10-15MPH) with at least 13 complete stops/starts for various intersections and traffic controls, and up to a bit over 19MPH peak speed here and there. Average on the PDA was about 12MPH, which includes longer-distance startups with the load in the pods on the way back.

Wh/mile wasn't nearly as good as I had expected based on analog panel meter readings and guesstimates. That panel meter is significantly low-reading, apparently, as I saw a bit more than half of the current readings on it as I do on this watt-meter.

For at least a very short time, there can be a peak of 105A battery side, driving the motor from stopped startup in a middle or high gear. That was on the way to work. In normal lower gears it's a peak of ~53A, on the way home from work, loaded up. That's using just the largest front ring (48T) and shifting between 6 rear rings from 28T up to 11T. The peaks must only a second at most, but that data isn't available from this meter--I'd need a Cycle Analyst and it's logging features to get that data.

Peak watts was 3281 on the way to work and 1784 on the way home.

Voltage dipped down to 31.11V on the way to work, and 39.11V on the way home. (No recharge between them, so must be caused by the high peak current drain at 105A.)

Total Ah usage was 1.905Ah on the way to work and 2.037Ah on the way home.

Oh, and as usual I run the lights all the time, day or night, which is another say, half an amp draw all the time, average, including the turn signal use. I don't currently have the lights wired in to the meter as I wanted to know only what the motor usage was first.

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